102results about How to "High field-effect mobility" patented technology

An object is to manufacture a semiconductor device including an oxide semiconductor at low cost with high productivity in such a manner that a photolithography process is simplified by reducing the number of light-exposure masks. In a method for manufacturing a semiconductor device including a channel-etched inverted-stagger thin film transistor, an oxide semiconductor film and a conductive film are etched using a mask layer formed with the use of a multi-tone mask which is a light-exposure mask through which light is transmitted so as to have a plurality of intensities. The etching step is performed by wet etching in which an etching solution is used.

A display device including an oxide semiconductor, a protective circuit and the like having appropriate structures and a small occupied area is necessary. The protective circuit is formed using a non-linear element which includes a gate insulating film covering a gate electrode; a first oxide semiconductor layer which is over the gate insulating layer and overlaps with the gate electrode; and a first wiring layer and a second wiring layer each of which is formed by stacking a conductive layer and a second oxide semiconductor layer and whose end portions are over the first oxide semiconductor layer and overlap with the gate electrode. The gate electrode of the non-linear element is connected to a scan line or a signal line, the first wiring layer or the second wiring layer of the non-linear element is directly connected to the gate electrode layer so as to apply potential of the gate electrode.

The protective circuit is formed using a non-linear element which includes a gate insulating film covering a gate electrode; a first wiring layer and a second wiring layer which are over the gate insulating film and whose end portions overlap with the gate electrode; and an oxide semiconductor layer which is over the gate electrode and in contact with the gate insulating film and the end portions of the first wiring layer and the second wiring layer. The gate electrode of the non-linear element and a scan line or a signal line is included in a wiring, the first or second wiring layer of the non-linear element is directly connected to the wiring so as to apply the potential of the gate electrode.

An object is to increase field effect mobility of a thin film transistor including an oxide semiconductor. Another object is to stabilize electrical characteristics of the thin film transistor. In a thin film transistor including an oxide semiconductor layer, a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor is formed over the oxide semiconductor layer, whereby field effect mobility of the thin film transistor can be increased. Further, by forming a semiconductor layer or a conductive layer having higher electrical conductivity than the oxide semiconductor between the oxide semiconductor layer and a protective insulating layer of the thin film transistor, change in composition or deterioration in film quality of the oxide semiconductor layer is prevented, so that electrical characteristics of the thin film transistor can be stabilized.

A light emitting device and an element substrate which are capable of suppressing variations in the luminance intensity of a light emitting element among pixels due to characteristic variations of a driving transistor without suppressing off-current of a switching transistor low and increasing storage capacity of a capacitor. According to the invention, a driving transistor also serves as an erasing transistor and the driving transistor is operated in a saturation region. The gate of the driving transistor is connected to an erasing scan line and it can be selected whether or not to flow current by a potential of the erasing scan line. In addition, a current controlling transistor which operates in a linear region is connected in series to the driving transistor, thus a video signal transmitting a light emission or non-emission of a pixel is input to the gate of the current controlling transistor through a switching transistor.

In order to take advantage of the properties of a display device including an oxide semiconductor, a protective circuit and the like having appropriate structures and a small occupied area are necessary. The protective circuit is formed using a non-linear element which includes a gate insulating film covering a gate electrode; a first oxide semiconductor layer over the gate insulating film; a channel protective layer covering a region which overlaps with a channel formation region of the first oxide semiconductor layer; and a first wiring layer and a second wiring layer each of which is formed by stacking a conductive layer and a second oxide semiconductor layer and over the first oxide semiconductor layer. The gate electrode is connected to a scan line or a signal line, the first wiring layer or the second wiring layer is directly connected to the gate electrode.